The chemical defense ecology of marine unicellular plankton: constraints, mechanisms, and impacts

The activities of unicellular microbes dominate the ecology of the marine environment, but the chemical signals that determine behavioral interactions are poorly known. In particular, chemical signals between microbial predators and prey contribute to food selection or avoidance and to defense, factors that probably affect trophic structure and such large-scale features as algal blooms. Using defense as an example, I consider physical constraints on the transmission of chemical information, and strategies and mechanisms that microbes might use to send chemical signals. Chemical signals in a low Re, viscosity-dominated physical environment are transferred by molecular diffusion and laminar advection, and may be perceived at nanomolar levels or lower. Events that occur on small temporal and physical scales in the "near-field" of prey are likely to play a role in cell-cell interactions. On the basis of cost-benefit optimization and the need for rapid activation, I suggest that microbial defense system strategies might be highly dynamic. These strategies include compartmented and activated reactions, utilizing both pulsed release of dissolved signals and contact-activated signals at the cell surface. Bioluminescence and extrusome discharge are two visible manifestations of rapidly activated microbial defenses that may serve as models for other chemical reactions as yet undetected due to the technical problems of measuring transient chemical gradients around single cells. As an example, I detail an algal dimethylsulfoniopropionate (DMSP) cleavage reaction that appears to deter protozoan feeding and explore it as a possible model for a rapidly activated, short-range chemical defense system. Although the exploration of chemical interactions among planktonic microbes is in its infancy, ecological models from macroorganisms provide useful hints of the complexity likely to be found.     

Climate change and marine plankton

Understanding how climate change will affect the planet is a key issue worldwide. Questions concerning the pace and impacts of climate change are thus central to many ecological and biogeochemical studies, and addressing the consequences of climate change is now high on the list of priorities for funding agencies. Here, we review the interactions between climate change and plankton communities, focusing on systematic changes in plankton community structure, abundance, distribution and phenology over recent decades. We examine the potential socioeconomic impacts of these plankton changes, such as the effects of bottom-up forcing on commercially exploited fish stocks (i.e. plankton as food for fish). We also consider the crucial roles that plankton might have in dictating the future pace of climate change via feedback mechanisms responding to elevated atmospheric CO(2) levels. An important message emerges from this review: ongoing plankton monitoring programmes worldwide will act as sentinels to identify future changes in marine ecosystems.     

Environmental influences on long-term variability in marine plankton

The major patterns of geographical and seasonal variability of the plankton of the north-east Atlantic and the North Sea are described to provide the background to a presentation of the dominant patterns of year-to-year fluctuations in the abundance of the plankton of the area for the period 1948 to 1984. A feature of the variability is a marked similarity both between species and between areas. The main pattern of year-to-year change has the form of a quasi linear downward trend in abundance with, superimposed on this, an element of variability with a periodicity of about three years. There is a complex relationship between the plankton and an estimate of changes in the frequency of westerly weather which can be interpreted in terms of influences acting over limited periods of the seasonal cycle coupled with persistence in the stocks of zooplankton. Relationships between year-to-year variations in the abundance of phytoplankton and zooplankton can be interpreted in terms of a response by the zooplankton to variations in food supply coupled with feed-back to the phytoplankton involving in situ nutrient regeneration.     

Community structure and function in prokaryotic marine plankton

Molecular biodiversity studies of microbial communities have provided invaluable information on the existence of heretofore unknown organisms and on community composition. Cloning and ‘fingerprinting’ techniques have been used many times to study prokaryote community composition of marine plankton. There are still many opportunities for new discoveries in this area, but the results have also opened new questions about the activities of these organisms and their function, going beyond just listing taxa or counting organisms. Rarely can the broad function be inferred from phylogenetic position alone (e.g. cyanobacteria). The recent discovery of abundant non-cyanobacterial marine phototrophs points to our inability to link phylogenetic position with function in a detailed way. One approach we have found fruitful is to combine fluorescence in situ hybridization with microautoradiography, a technique dubbed STARFISH. A recent application has shown that ubiquitous archaea from the deep sea, phylogenetically related to extreme thermophiles, are active in the uptake of amino acids from ambient (nanomolar) concentrations. This suggests the group is at least partly heterotrophic and able to compete successfully with bacteria for nutrients. Other as-yet uncultivated groups are also amenable to similar studies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Prokaryotic and viral diversity patterns in marine plankton

Prokaryotes and viruses play critical roles in marine ecosystems, where they are both highly abundant and active. Although early work on both prokaryotes and viruses revealed little of their diversity, molecular biological approaches now allow us to break apart these black boxes. The most revealing methods have been cloning and sequencing of 16S rRNA genes, community fingerprinting (such as terminal restriction fragment length polymorphism; TRFLP), and fluorescent in situ hybridization. Viral diversity can now be analyzed by pulsed field gel electrophoresis (PFGE) of viral genomes. The present paper summarizes recent advances in bacterial and virus diversity studies, and presents examples of measurements from polar, tropical, and temperate marine waters. Terminal restriction fragment length polymorphism shows that many of the same operationally defined prokaryotic taxa are present in polar and tropical waters, but there are also some unique to each environment. By one measure, a sample from over a Philippine coral reef had about 100 operationally defined taxa, whereas one from the open tropical Atlantic had about 50 and from the icy Weddell Sea, about 60. Pulsed field gel electrophoresis of two depth profiles, to 500 m, from Southern California, measured 2 months apart, shows striking similarities in viral genome length diversity over time, and some distinct differences with depth. The euphotic zone samples had extremely similar apparent diversity, but samples from 150 m and 500 m were different. An obvious next step is to compare the bacterial and viral diversity patterns, because theory tells us they should be related.     

Fishing impacts on the marine inorganic carbon cycle

1.  Teleost fish excrete precipitated carbonate and make significant contributions to the marine inorganic carbon cycle at regional and global scales. As total carbonate production is linked to fish size and abundance, fishing is predicted to affect carbonate production by modifying fish abundance and size-structure.
2.  We draw on concepts from physiology, metabolic ecology, life history theory, population dynamics and community ecology to develop, validate and apply analytical tools to assess fishing impacts on carbonate production. Outputs suggest that population and community carbonate production fall rapidly at lower rates of fishing than those used as management targets for sustainable yield.
3.  Theoretical predictions are corroborated by estimated trends in carbonate production by a herring population and a coral reef fish community subject to fishing. Our analytical results build on widely applicable relationships between life history parameters and metabolic rates, and can be generalized to most fished ecosystems.
4.   Synthesis and applications . If the maintenance of chemical processes as well as biological process were adopted as a management objective for fisheries then the methods we have developed can be applied to assess the effects of fishing on carbonate production and to advise on acceptable rates of fishing. Maintenance of this ecosystem service would require lower rates of fishing mortality than those recommended to achieve sustainable yield.     

Simulated annual plankton production in the northeastern Pacific Coastal Upwelling Domain

A microcomputer simulation model is presented that describesthe generalized plankton production dynamics, in the surfacemixed layer, of the Juan de Fuca Eddy located on the southwesternBritish Columbia continental shelf. The Juan de Fuca Eddy simulationmodel evaluates how the annual biomass production of diatoms,copepods and euphausiids is forced by plankton feeding interactions,seasonal variability in upwelling, water temperature and solarradiation, and generalized fish predation. The model estimatesannual primary production of 345 g C m^–2 year^–1and secondary production of 19.4 g C m^–2 year^–1for copepods and 6 g C m^–2 year^–1 for euphausiids,during 1985–89; -90% of the annual plankton productionwas generated during the April-October upwelling season. Perturbationsof 22 abiotic and biotic parameters, one at a time by ±10%of nominal values, indicated that oceanic variability (e.g.upwelling rate) most strongly affected primary production. Conversely,zooplankton production was most sensitive to variability inbiological parameters describing zooplankton grazing potentialand growth (e.g. gross growth efficiency). Simulated seasonalbiomass patterns of diatoms, copepods and euphausiids were foundto closely match empirical data. However, euphausiid biomassproduction in the Juan de Fuca Eddy alone was unable to meetthe demands of estimated pelagic fish consumption. Local Eddyeuphausiid populations had to be supplemented, from regionaleuphausiids. by a mechanism that is proposed to be linked tothe seasonal pattern and intensity of positive Ekman transport(upwelling).     

Defining seasonal marine microbial community dynamics

Here we describe, the longest microbial time-series analyzed to date using high-resolution 16S rRNA tag pyrosequencing of samples taken monthly over 6 years at a temperate marine coastal site off Plymouth, UK. Data treatment effected the estimation of community richness over a 6-year period, whereby 8794 operational taxonomic units (OTUs) were identified using single-linkage preclustering and 21 130 OTUs were identified by denoising the data. The Alphaproteobacteria were the most abundant Class, and the most frequently recorded OTUs were members of the Rickettsiales (SAR 11) and Rhodobacteriales. This near-surface ocean bacterial community showed strong repeatable seasonal patterns, which were defined by winter peaks in diversity across all years. Environmental variables explained far more variation in seasonally predictable bacteria than did data on protists or metazoan biomass. Change in day length alone explains >65% of the variance in community diversity. The results suggested that seasonal changes in environmental variables are more important than trophic interactions. Interestingly, microbial association network analysis showed that correlations in abundance were stronger within bacterial taxa rather than between bacteria and eukaryotes, or between bacteria and environmental variables.     

On the life history of the marine plankton diatomStephanopyxis palmeriana

Summary 1. The cell diameter ofStephanopyxis palmeriana ranges between 19 and 156µ. The pleural structure is considered to be specific for the genus. The interphasic nucleus lies in the discus of the hypovalva.2. The cell size can be manipulated during the vegetative phase through SiO₂-deficiency followed by frustule regeneration.3. Only 19 to 60µ wide cells are capable of forming gametes and auxospores. Differentiation begins after light intensity is suddenly increased from 400 to 4000 Lux, and temperature from 15° to 21° C.4. Only 19 to 90µ wide cells are capable of forming resting spores. These are produced in the presence of phosphate-deficiency; maximum production occurs at 12° C. After correction of the phosphate-deficiency, resting spores germinate.5. Morphologically, the life history (formation of gametes, auxospores, resting spores) conforms essentially with the findings onStephanopyxis turris (v.Stosch &Drebes 1964).6. The most important factors controlling the life cycle are cell size, temperature, light and nutrients. The effects which these factors produce inS. turris are compared with those observed inS. palmeriana.

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Zur Entwicklungsgeschichte der marinen PlanktondiatomeeStephanopyxis palmeriana

Kurzfassung Im Frühjahr 1964 wurde die zentrische PlanktondiatomeeStephanopyxis palmeriana (Grev.)Grunow — eine aus japanischen Gewässern stammende Warmwasserform und unsererS. turris sehr nahe verwandt — in Kultur genommen. Schon nach kurzer Zeit war es möglich, den gesamten Formwechsel dieser Alge in seinen Grundzügen kennenzulernen. Mit Hilfe von Wasserimmersionen konnten in direkter Lebendbeobachtung Zellteilung, Meiosis, Befruchtung und Auxosporenbildung mit ihren metagamen Mitosen sowie die Bildung und Keimung der Dauersporen studiert werden. Morphologisch stimmt der Formwechsel mit dem vonS. turris (v.Stosch &Drebes 1964) überein; in der Abhängigkeit von Umweltfaktoren bestehen jedoch Unterschiede. So werden Dauersporen bei dieser zwischen 19 und 156µ Zellbreite (= Transversaldurchmesser) vegetativ existierenden Alge nur von schmalen, unter 90µ breiten Zellen in Gegenwart von Phosphatmangel (spärlich manchmal auch bei Nitratmangel) differenziert. Eine Temperatur von 12° C wirkt dabei sehr begünstigend. Die Keimung der Dauersporen setzt nach Beseitigung des Phosphatmangels ein. Zur Sexualisierung sind nur unter 60µ breite Zellen fähig; sie findet statt nach sprunghafter Steigerung der Beleuchtungsstärke (von 400 auf 4000 Lux) sowie einer Temperaturerhöhung von 15° auf 21° C. Wegen der Dickschaligkeit bereitet die Änderung der Zellgröße auf künstlichem Wege durch SiO₂-Mangel mit nachfolgender Schalenregeneration einige Schwierigkeiten. Diese Manipulationen sind jedoch notwendig, wenn ein Klon ohne Veränderung seines Idiotypus über die Auxospore für unbegrenzte Dauer zur Verfügung stehen soll.

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The studies were carried out in the Botanical Institute of the University, Marburg.     

High local and global diversity of Flavobacteria in marine plankton

Members of the phylum Bacteroidetes are among the most abundant microbes in coastal marine waters, but it is unclear to which extent the diversity within this phylum is covered by currently available 16S rRNA gene sequence information. We, thus, obtained a comprehensive collection of sequence types affiliated with Bacteroidetes in coastal North Sea surface waters and we compared this local diversity with the available sequences of marine planktonic and other aquatic Bacteroidetes. Approximately 15% of > 600 clones from two libraries (August 2000, June 2001) were related to Bacteroidetes, specifically to the Flavobacteria. Local diversity appeared to be almost exhaustively sampled. However, the diversity of the two libraries virtually did not overlap, indicating a pronounced temporal variability of the planktonic Flavobacteria assemblage. The majority of sequence types represented novel phylogenetic lineages, adding 6-7% to the currently known genera and species of Bacteroidetes in marine waters. Different diversity estimators suggested that so far only approximately half of the global diversity of planktonic marine Bacteroidetes has been described. The data set moreover indicated that cultivation-independent techniques and isolation approaches have recovered almost equally sized and virtually non-overlapping fractions of the currently known diversity within this phylum. Interestingly, only 15% of genera of Bacteroidetes from various aquatic environments appear to occur in more than one habitat type.     

Preservation potential of ancient plankton DNA in Pleistocene marine sediments

Recent studies have shown that ancient plankton DNA can be recovered from Holocene lacustrine and marine sediments, including from species that do not leave diagnostic microscopic fossils in the sediment record. Therefore, the analysis of this so-called fossil plankton DNA is a promising approach for refining paleoecological and paleoenvironmental information. However, further studies are needed to reveal whether DNA of past plankton is preserved beyond the Holocene. Here, we identified past eukaryotic plankton members based on 18S rRNA gene profiling in eastern Mediterranean Holocene and Pleistocene sapropels S1 (~9 ka), S3 (~80 ka), S4 (~105 ka), and S5 (~125 ka). The majority of preserved ~400- to 500-bp-long 18S rDNA fragments of microalgae that were studied in detail (i.e. from haptophyte algae and dinoflagellates) were found in the youngest sapropel S1, whereas their specific lipid biomarkers (long-chain alkenones and dinosterol) were also abundant in sediments deposited between 80 and 124 ka BP. The late-Pleistocene sediments mainly contained eukaryotic DNA of marine fungi and from terrestrial plants, which could have been introduced via the river Nile at the time of deposition and preserved in pollen grains. A parallel analysis of Branched and Isoprenoid Tetraethers (i.e. BIT index) showed that most of the organic matter in the eastern Mediterranean sediment record was of marine (e.g. pelagic) origin. Therefore, the predominance of terrestrial plant DNA over plankton DNA in older sapropels suggests a preferential degradation of marine plankton DNA.     

Modelling environmental impacts of marine finfish aquaculture

Our understanding of the interactions between fish farms and the environment has reached the stage where it is reasonable to expect that quantitative estimates of the possible environmental consequences of aquaculture development can be provided for regulatory and mitigation purposes. This paper summarizes recent developments in this area and provides several case histories of areas where theoretical analyses appear to have direct practical relevance.     

Observations of bioluminescence in marine plankton from the Sea of Cortez

A bioluminescence chemical oceanography research cruise (Varifront III) through the Sea of Cortez from November through December 1981 provided an opportunity to investigate plankton associated with a brilliant and extensive display of surface water bioluminescence at the north end of Balleñas Channel. New observations of bioluminescence were made on larval stages of the euphausiid Nyctiphanes simplex Hansen (Calyptopis II, Furcilia I, II, and III, and juveniles) and Euphausia eximia Hansen (Calyptopis I), the Calanoida copepods Centropages furcatus Dana, Paracalanus indiens Wolfenden, Acrocalanus longicornis Giesbrecht, the Cyclopoida copepods Corycaeus (Corycaeus) speciousus Dana, Corycaeus (Onychocorycaeus) latus Dana, and several dinoflagellates Ceratium breve Ostenfeld and Schmidt, Ceratium horridum Gran, and Ceratium gibberum Gourret. These observations indicate the increasing importance of some of the smaller copepods and larval euphausiids contributing to surface bioluminescence.     

some aspects of the biochemical and mineral composition of marine plankton

A natural population of phytoplankton and two species of zooplankton, Calanus finmarchicus (Gunnerus) (stage V) and Sagitta elegans (Verrill) (mature), were analysed for their biochemical and mineral composition. Comparison with published data for the same categories of plankton shows that the distribution of both organic and mineral fractions is highly variable, the causes of which are not equally understood. The composition of the organic fraction is affected by the duality of function of the biochemical constituents and by the large number of ecological factors which influence their concentration. Whether this applies to the mineral fraction remains uncertain; nevertheless it appears that plankton concentrate trace metals, that phytoplankton has a greater ability to concentrate them than zooplankton, and that the ability of zooplankton to concentrate various metals varies with the species.     

Interannual variability in the seasonal plankton succession of a shallow, warm-water lake

Common seasonal plankton succession patterns in temperate lakes are well understood, and were described in the popular PEG-model. Seasonal plankton succession in warm-water lakes, however, is not as well known. Recent theory suggests that some lake systems are characteristic of having alternate system-states, where one of the system-states is characterized by dominance of cyanobacteria, and transition between system-states can be abrupt and undeterminable. Lake Somerville, a shallow, well-mixed, warm-water reservoir located in eastern TX, U.S.A., experiences occasional periods of cyanobacteria dominance. To increase our understanding of seasonal plankton dynamics in warm-water systems, we analyzed 14-years of plankton data spanning a 22-year period. During this period, succession dynamics characteristic of those described by the PEG-model were observed, as well as succession dynamics expected during periods of cyanobacteria dominance, i.e., greater accumulated phytoplankton biovolume, low secondary productivity, and low light penetration. In addition to the PEG-model and cyanobacteria type system-states, other states of the system that were intermediate between these were observed. Therefore, we conclude the lake does not behave according to the alternate system-states model. The change from year to year in early-year cyanobacteria dominance was abrupt and non-monotonic during this period. In addition, the early year performance of cyanobacteria appeared to influence the plankton succession trajectory for the remainder of the season. While the magnitude of lake-flushing early in the year accounted for ～37% of variability in cyanobacteria prevalence, many of the traditional factors impacting cyanobacteria dominance appeared insignificant.     

The potential impacts of global climate change on marine protected areas

The potential effects of global climate changeon marine protected areas do not appear to havebeen addressed in the literature. This paperexamines the literature on protected areas,conservation biology, marine ecology,oceanography, and climate change, and reviewssome of the relevant differences between marineand terrestrial environments. Frameworks andclassifications systems used in protected areadesign are discussed. Finally, a frameworkthat summarizes some of the importantoceanographic processes and their links to thefood chain are reviewed. Species abundance anddistribution are expected to change as a resultof global climate change, potentiallycompromising the efficacy of marine protectedareas as biodiversity conservation tools. Thisreview suggests the need for: furtherinterdisciplinary research and the use oflinked models; an increase in marine protectedareas for biodiversity conservation and asresearch sites for teasing apart fishingeffects from climate effects; a temporallyresponsive approach to siting new marineprotected areas, shifting their locations ifnecessary; and large-scale ecosystem/integratedmanagement approaches to address the competinguses of the oceans and boundary-less threatssuch as global climate change and pollution.     

Disrupted seasonal biology impacts health,food security and ecosystems

The rhythm of life on earth is shaped by seasonal changes in the environment. Plants and animals show profound annual cycles in physiology, health, morphology, behaviour and demography in response to environmental cues. Seasonal biology impacts ecosystems and agriculture, with consequences for humans and biodiversity. Human populations show robust annual rhythms in health and well-being, and the birth month can have lasting effects that persist throughout life. This review emphasizes the need for a better understanding of seasonal biology against the backdrop of its rapidly progressing disruption through climate change, human lifestyles and other anthropogenic impact. Climate change is modifying annual rhythms to which numerous organisms have adapted, with potential consequences for industries relating to health, ecosystems and food security. Disconcertingly, human lifestyles under artificial conditions of eternal summer provide the most extreme example for disconnect from natural seasons, making humans vulnerable to increased morbidity and mortality. In this review, we introduce scenarios of seasonal disruption, highlight key aspects of seasonal biology and summarize from biomedical, anthropological, veterinary, agricultural and environmental perspectives the recent evidence for seasonal desynchronization between environmental factors and internal rhythms. Because annual rhythms are pervasive across biological systems, they provide a common framework for trans-disciplinary research.     

Continuous plankton records: seasonal variations in the distribution and abundance of plankton in the North Atlantic Ocean and the North Sea

Charts are presented of the seasonal variations in the distributionof four phytoplankton and five zooplankton taxa in the NorthAtlantic and the North Sea. The main factors determining theseasonal variations appear to be the distribution of the mainoverwintering stocks, the current system and, in some instances,temperature control of the rate of population increase. Informationis presented about the variation with latitude (over the rangefrom 34° N to 65 ° N) of the seasonal regime of theplankton. On the assumption that there is a relationship betweennutrient supply and vertical temperature stratification themain features of this variability can be interpreted. In thesouth (to about 43° N) nutrient limitation plus grazingappear to be dominant, resulting in a bimodal seasonal cycleof phytoplankton. North of about 60° N the system appearsto be limited by the size of the phytoplankton stocks beinggrazed primarily by Calanus Finmarchicus and Euphausiacea. Inan extensive zone, from about 44° N to 60° N, it wouldappear that the spring bloom of phytoplankton is under-exploitedby grazing while in summer the zooplankton graze the daily productionof the phytoplankton, the stocks of which are probably maintainedby in situ nutrient regeneration. The implications, for at leastthis mid-latitude zone, that rates and fluxes of processes,as opposed to density dependent interactions between stocks,play a major role in the dynamics of the seasonal cycle is consistentwith previously reported observations suggesting that physicalenvironmental factors play a major role in determining year-to-yearfluctuations in the abundance of the plankton.     

The potential impacts of global climate change on marine protected areas

Reviews in Fish Biology and Fisheries - The potential effects of global climate changeon marine protected areas do not appear to havebeen addressed in the literature. This paperexamines the...     

采矿业对赞比亚的社会经济及环境的影响

采矿业是赞比亚一类非常重要的工业 ,大量的开采和选矿作业给周边地区带来了严重的环境问题。导致了该区域内地表水、空气、土壤的污染 ,并对当地人民的身体健康带来威胁。本文主要分析铜矿开采业对赞比亚的社会经济及环境的影响 ,进一步探讨可以保持当地采矿业的可持续发展的有效措施。